Lead leaching into soil or water is a universal problem. There are many uses for lead, some of which are difficult to replace either economically or in performance. One is the use of lead in sporting and military ammunition. If ammunition could be fabricated from elements with nearly the same ballistic performance and economical cost as lead, the problems of lead leaching could be avoided. Unfortunately, in both performance and cost, lead is difficult to match. Thus an efficient and economical way to inhibit lead leaching in fabricating structure containing lead is desirable.
An approach to inhibiting lead leaching in bullets is found in U.S. Pat. No. 6,095,052, Corrosion Resistant Metal Body, Bullet Blank, and Bullet and Method for Making Same, to Bean et al., Aug. 1, 2000, incorporated herein by reference. The '052 patent describes the fabrication and structure of a composite bullet core consisting of a thick lead sheet covered by one or two thin zinc sheets or coatings. If two zinc sheets or coatings are used one would cover the top of the lead sheet and the other the bottom. In its most basic form, the '052 bullet core is formed by placing a thin zinc sheet over a thicker lead sheet and rolling the adjacent metal layers into a cylinder having the thin zinc sheet on the outside. This may be augmented by placing a thin zinc sheet on the reverse side also. The resultant cylinder may be pressed into any desired shape in a die and enclosed in a traditional bullet jacket, such as copper or copper alloy, to yield a finished jacketed bullet.
Although the bullet fabricated according to the method of the '052 patent affords measurable environmental benefits as compared to a conventional lead or lead-alloy bullet core, the possibility exists for lead or lead-alloy fragments to separate from the zinc sheets within the bullet upon impact. Thus what is needed is a lead or lead-alloy composite structure that under its normal use does not result in immediate exposure of a lead or lead-alloy surface to the environment. A preferred embodiment of the present invention affords this protection via use of fine zinc or zinc-alloy plated lead or lead-alloy wires as the base elements of structure formed by compressing a number of these fine wires into a solid of a pre-specified shape. A number of patents have addressed one or more aspects of the approach taken by the present invention. None have zinc or zinc-alloy plated fine lead or lead-alloy wire for use as a component of structure.
U.S. Pat. No. 4,411,742, Electrolytic Codeposition of Zinc and Graphite and Resulting Product, to Donakowski et al., Oct. 25, 1983, details a process for codepositing zinc and graphite on a substrate, and is incorporated herein by reference. The graphite is in the form of insoluble bulk graphite that is agitated in the same electrolysis tank as the zinc. The resultant surface has greatly improved corrosion resistance.
U.S. Pat. No. 4,881,465, Non-Toxic Shot Pellets for Shotguns and Method, to Hooper et al., Nov. 21, 1989, describes a pellet having ballistic characteristics similar to lead pellets but fabricated of an alloy of ferrotungsten suspended in a matrix of an alloy of mostly tin, antimony and lead, mostly lead. Since this pellet has less than 40% lead, it has been labeled non-toxic for its intended use.
U.S. Pat. No. 5,088,415, Environmentally Improved Shot, to Huffman et al., Feb. 18, 1992, provides shot with a density comparable to lead but less toxic because it has been coated with a chemically inert polymer. This shot is available in three forms. The first is polymer coated lead shot that is heated to above the melting point of the lead while otherwise maintaining its shape to both mechanically and chemically bond the polymer coating. The second form employs a metal with a density greater than lead, such as depleted uranium, coated with a metal such as zinc, bismuth, aluminum, tin, copper, iron, nickel or their alloys. The third form involves melting any of the lighter metals and adding powdered heavier metals such as tungsten or depleted uranium. Only the first form is claimed in the claims.
U.S. Pat. No. 5,439,713, Steel Wire Coated with Fe—Zn—Al Alloys and Method for Producing the Same, to Yamaoka et al., Aug. 8, 1995, uses a two-part immersion in a zinc molten bath followed by a zinc-aluminum molten bath to form the ternary Fe—Zn—Al coating on wire to be used to make strong corrosion resistant springs.
U.S. Pat. No. 5,569,874, Formed Wire Bullet, to Nelson, Oct. 29, 1996, describes a bullet formed in an entwined composite mass from a number of “elongate malleable elements” devoid of lead, e.g., copper wires. The wires are “woven” in a pre-specified pattern to form a bullet core. The wires are not described nor claimed as being coated or electroplated. A main attribute and claim, although not the basic claim, is that the wire contains no lead.
U.S. Pat. No. 5,618,634, Composite Zinc- or Zinc Alloy-Electroplated Metal Sheet and Method for the Production Thereof, to Hosoda et al., Apr. 8, 1997, incorporated herein by reference, describes an electroplated metal sheet and a plating solution that contains at least one organic compound to co-deposit carbon up to 10 wt-%. It yields improved post-painting corrosion resistance, press formability, and spot weldability. This composite zinc plating resists “powdering” during press forming.
U.S. Pat. No. 6,024,021, Fragmenting Bullet, to Schultz, Feb. 15, 2000, describes a bullet comprising a core of compressed lead rods surrounded by a copper jacket. The lead rods are not coated or electroplated.
U.S. Pat. No. 6,162,508, Molybdenum Phosphate Based Corrosion Resistant Conversion Coatings, to Trumble et al., Dec. 19, 2000, incorporated herein by reference, describes a molybdenum phosphate coating for zinc or zinc-alloy plated substrates that both significantly increases corrosion resistance and is a replacement for chromate coatings.
U.S. Pat. No. 6,173,652 B1, Environmentally Sealed Shot, to Taylor, Jan. 16, 2001, describes lead shot sealed on its exterior by a non-toxic layer that is resilient. One of the items in the coating used to seal the shot and make it “abhorrent” to birds is chili.
As applied specifically to bullets or bullet cores, corrosion resistant lead structure should have approximately the same ballistic performance as a conventional lead or lead alloy core. Thus, the amount of plating or coating of the lead should be minimized to facilitate ballistic performance, while optimized to enhance corrosion resistance. Further, although the cost of producing the “environmentally friendly” bullet of the present invention exceeds that of traditional lead or lead alloy bullets or bullet cores, it should be significantly less than for alternatives to lead or lead alloy such as tungsten, tantalum, tin, iron, polymers or alloys and combinations thereof. Preferred embodiments of the present invention address these requirements.